In an effort to minimize deleterious air flow in the hollow pillars, and particularly the "A" pillars because they are the ones most susceptible to generation of undesirable wind noises, a hose for conducting sealer in fluid form was inserted into each of the pillar interior access holes. A pumpable, expandable sealer was then pumped into the void portion of the pillar. This was initially done after the pillars had been assembled to the rest of the body. It was also commonly done after the electro-coated paint had been applied and cured. The sealer would have certain ingredients mixed together physically just prior to the point of its being pumped into the pillars, the various ingredients reacting so that the sealer expanded soon thereafter.
The time for the beginning of such reaction had to be controlled as carefully as possible, because the sealer had to retain fluid flow characteristics until the void or cavity of each pillar was sufficiently filled to have a reasonable success rate of blocking it. However, because of this need for retention of the sealer fluid flow characteristics, some of the sealer sometimes flowed on through and out of a pillar before the sealer had properly expanded and lost its fluid flow characteristics, leaving a hole through the length of the pillar through which air could still flow and which would also contribute the entrance and consequent retention of moisture. At times, such a hole would actually increase the audible noise generated by air flow through the pillar, much like a whistle, thus abetting the very condition which it should have alleviated.
The needed retention of the sealer fluid flow characteristics, coupled with the all-too-often flow of the sealer through the length of the pillars, led to orienting each pillar section to be sealed to a position which would place at least a sealable part of the pillar void or cavity at the lowest level while the sealer expanded. This had to be done before the pillar section was assembled to other parts of the vehicle body, and therefore before the electro-coating and baking process was done. The sealer then covered areas of the interior surfaces of the pillar so that they were not later electro-coated with rust inhibitors, leaving such areas vulnerable to rust should the sealer not strongly adhere to those surfaces for the life of the vehicle.
Thus this practice, while better than no effort, was not fully satisfactory, and was time-consuming and more costly than desirable.
Another attempt to solve the air flow and rust problems has involved the use of a heat-expandable sealer introduced into the appropriate cavities which did not require premixing immediately before such introduction, and did not require careful control of the expansion and curing of the sealer from the time of introduction because the sealer was expanded and cured by heat applied to the vehicle body section during paint drying and curing. However, the sealer still had to be introduced with sufficient flow characteristics, whether in the form of a liquid or a powder-like solid which will flow like a liquid, to be placed in the cavities from the point of introduction. Like the above-noted practice, this sealer also sought lower levels which were not the proper locations for the sealer, and also at times flowed on through and out of the cavities, leaving passageways through the cavities through which air and other fluids could still pass. While this solved some of the application problems, it still did not satisfactorily solve all of the problems being encountered.